1. The Field of the Invention
The present invention relates to compositions and methods for whitening and desensitizing teeth. The present invention relates to compositions that may be applied directly to a person""s teeth for shorter periods of time, and those specifically formulated for use with flexible, thin-walled dental trays in order to provide prolonged treatment of a patient""s teeth over longer periods of time.
2. The Relevant Technology
The use of certain foods and tobacco, the process of aging, diseases, trauma, medications, some congenital conditions, and environmental effects can cause teeth to become discolored. Because teeth without discolorations are usually considered to be aesthetically superior to stained or discolored teeth, there has been a heightened level of interest of late in developing compositions and methods for bleaching teeth.
A tooth is comprised of an inner dentin layer and an outer hard enamel layer that is slightly porous. The outer layer is the protective layer of the tooth. The natural color of the tooth is opaque to translucent white or slightly off-white.
Some dental compositions like dentrifices, toothpastes, gels, and powders contain active oxygen or hydrogen peroxide liberating bleaching agents. Such bleaching agents include peroxides, percarbonates and perborates of the alkali and alkaline earth metals or complex compounds containing hydrogen peroxide. Also, peroxide salts of the alkali or alkaline earth metals are known to be useful in whitening teeth.
The most commonly used dental bleaching agent is carbamide peroxide (CO(NH2)2.H2O2), also called urea hydrogen peroxide, hydrogen peroxide carbamide, and perhydrol-urea. Carbamide peroxide has been used by dental clinicians for several decades as an oral antiseptic. Tooth bleaching was an observed side effect of extended contact time. Over-the-counter compositions of 10% carbamide peroxide are available as GLY-OXIDE(copyright) by Marion Laboratories and PROXIGEL(copyright) by Reed and Carnrick. A bleaching gel which is able to hold a comfortable-fitting dental tray in position for an extended time period is available under the trademark OPALESCENCE(copyright) from Ultradent Products, Inc. in South Jordan, Utah. Other bleaching agents such as peroxyacetic acid (CH3Cxe2x95x90OOxe2x80x94OH) and sodium perborate, are also known in the medical, dental and cosmetic arts.
Patients who have desired to have their teeth whitened have typically done so by applying a bleaching composition to the teeth by means of a dental tray for repeated treatments, or they have had to submit to conventional in-office bleaching techniques that required from 4 to 10 visits to the dental office before clinically significant results were achieved. Clinically significant results are quantifiable such as by measuring gray scale, L*, and as to yellowness or blueness, b*, in the CIE(copyright) system of color measurement or by equivalent methods.
Patients expecting their teeth to be whitened by such bleaching treatments may be pleased to have their stains removed, however, a more ideal aesthetic objective of whiter teeth may still not be adequately achieved. The removal of stains and discolorations sometimes reveal that the stains camouflaged teeth which are excessively translucent. Depending on the degree of translucency, the teeth may be revealed to be overly grey or even have portions which appear to be more transparent than is desired.
Brushing teeth with toothpaste does not address the problem of excessively translucent teeth. Brushing teeth with toothpastes or polishes is also less effective for whitening teeth compared to the application of bleaching treatments. Tooth brushing is less effective for whitening teeth as brushing teeth only cleans the external surface of the teeth while bleaching addresses internal stains in the teeth.
From the foregoing, it will be appreciated that what is needed in the art are compositions and methods for opacifying and decreasing the transparency of teeth.
It will also be appreciated that what is also needed are methods and compositions for opacifying teeth and whitening teeth without causing teeth to become overly sensitized.
What are also need are compositions and methods which are able to bleach teeth while concurrently offsetting the tendency of bleaching agents to cause teeth to become overly sensitive.
The present invention generally relates to dental whitening compositions and methods for treating excessively translucent teeth. In addition, the present invention relates to bleaching compositions that result in reduced sensitivity. The present invention utilizes potassium nitrate (KNO3) dispersed within a carrier as an opacifying agent to reduce the tendency of some teeth to appear grey or translucent. Potassium nitrate can act as an opacifying agent either alone or in combination with a bleaching agent. Because potassium nitrate also has desensitizing or anesthetic properties, it can desensitize and/or opacify when used in conjunction with a bleaching agent, or it can be applied separately to desensitize teeth after bleaching has occurred.
In addition to potassium nitrate, other dental agents may be dispersed in the carrier. In one embodiment, the whitening compositions will include a bleaching agent, such as carbamide peroxide, which can also act as a disinfectant. Alternatively, or in addition to including a bleaching agent, the whitening compositions may include one or more other dental agents, such as anticariogenic agents for reinforcing teeth against tooth decay or antimicrobial agents for treating gum diseases. The most commonly used anticariogenic agents include fluoride salts, such as stannous or sodium fluoride, which can also impart antidemineralization or even remineralization properties to the tooth whitening compositions. Examples of preferred antimicrobial agents include chlorohexidine, tetracycline, cetyl pyridinium chloride, benzalkonium chloride, cetyl pyridinium bromide, methyl benzoate, and propyl benzoate.
The compositions are preferably substantially free of abrasives, as the compositions are typically not scrubbed onto teeth. When using abrasive toothpastes, people typically brush for less than 60 seconds, which is not enough time for the active ingredients to perform their intended activity. On the other hand, scrubbing teeth with an abrasive material for an extended period of time can be harnful in some cases. Therefore, in order to allow for extended application, the inventive compositions will preferably not include substantial quantities of an abrasive.
The compositions are preferably used with a dental tray that is thin-walled, flexible and lightweight. Such trays can be held by the dental composition in position adjacent to the person""s tooth surfaces to be treated. The preferred dental tray should be adapted for maximum comfort and will exert little if any significant mechanical pressure onto the person""s teeth or gums. Accordingly, when used with a tray, the dental whitening compositions will preferably be sufficiently sticky, viscous and resistant to dilution by saliva such that they can act as a glue and reliably adhere and retain the dental tray over the person""s teeth for varying time durations. Nevertheless, although such dental trays are preferred, any conventional dental trays may also be utilized. In addition, the inventive dental compositions can be applied directly to a person""s teeth without a tray. In such cases, higher concentrations of the dental agent(s) will preferably be used in order to speed up the desired action or results of the dental agent(s).
Any component other than the active dental agents, such as the potassium nitrate, bleaching agent, antimicrobial agent, and anticariogenic agent, shall comprise the xe2x80x9ccarrierxe2x80x9d. In the case where the dental composition is sticky and viscous, the carrier will include a sticky matrix material formed by combining a sufficient quantity of a tackifying agent, such as carboxypolymethylene, with a solvent, such as glycerin, polyethylene glycol, or water. Although the carrier is preferably formed by combining a tackifying agent and a solvent, the carrier may comprise a solvent without a tackifying agent in some embodiments. Preferred compositions, as described hereinbelow, are relatively sticky and glue-like to enable a preferred dental tray to be held and retained against a person""s teeth. Preferred carriers are preferably safe for oral use, do not readily dissolve in saliva, and do not react with the tooth opacifying agent.
In addition to carboxypolymethylene, examples of other suitable tackifying agents, or thickening agents that can assist other tackifying agents, include xanthan gum, talha gum, tragacanth gum, carboxymethylcellulose, locust bean gum, guar gum, Irish moss gum, ghatti gum, furcelleran gum, carrageenan gum, arabic gum, alginic acid gum, agar gum, alginate gum, PEMULEN(copyright), a proprietary compound of B.F. Goodrich, POLYOX(copyright), a mixture of polyethylene oxides having a molecular weight of 100,000-8,000,000 and available from Union Carbide, or any compositional or chemical equivalents of the foregoing. PEMULEN(copyright) is a propriety formula that includes a significant quantity of a polyacrylic copolymer that has a slightly hydrophobic end and a strongly hydrophilic end.
In addition to glycerin, many other polyols may serve as suitable solvents. The solvent may also be water alone or in combination with a polyol. Glycerin is a preferred solvent as it works well in forming a sticky gel with carboxypolymethylene. Glycerin also provides some flavor enhancement. A few possible substitutes for glycerin include propylene glycols, polypropylene glycol, polyethylene glycols, eryrthritol, sorbitol, mannitol, other polyols, and the like. In some embodiments polyols such as glycerin, polyethylene glycols, polypropylene glycol, propylene glycol, and sorbitol may also be used without a tackifying agent.
As indicated hereinabove, one currently preferred sticky matrix material includes a mixture of carboxypolymethylene together and other suitable admixtures. The term xe2x80x9ccarboxypolymethylenexe2x80x9d is used to denote a broad category of polymers, particularly copolymers of acrylic acid and polyallyl sucrose. Because carboxypolymethylene that has not been completely neutralized includes carboxylic acid groups or moieties, carboxypolymethylene can be classified as a weak acid. When dispersed in water, carboxypolymethylene can have a pH as low as about 2.5.
Because highly acidic compositions can etch teeth, it is generally preferable to adjust the pH of dental compositions that include carboxypolymethylene or other acids to make them less acidic. Accordingly, it is preferable to adjust the pH of compositions that include carboxypolymethylene to within a range from about 4 to about 9, more preferably to within a range from about 5 to about 7. Because it is contemplated that the carboxypolymethylene used in the matrix material and the compositions of the present invention will be mixed with a base to raise the pH of the resulting dental composition, the term xe2x80x9ccarboxypolymethylenexe2x80x9d shall include carboxypolymethylene polymers within compositions at any pH.
The matrix material can include other optional components in addition to the carboxypolymethylene in order to provide bulk and also to yield a matrix material having the desired level of stickiness. One such admixture is glycerin, which is easily mixed with carboxypolymethylene. Another optional component is water, as set forth above. It is preferable to use a base in order to adjust the pH of the matrix material. Preferred bases can include inorganic bases such as sodium hydroxide or ammonium hydroxide. Alternatively, the base may include an organic base such as triethanolamine or other organic amines.
Since peroxides may cause irritation and also greater sensitivity in teeth for some people, the simultaneous inclusion of potassium nitrate can offset the potentially negative effects of the peroxide. Accordingly, potassium nitrate can simultaneously provide both opacification and desensitization. Other desensitizing agents can also be used to desensitize teeth, including citric acid, citric acid salts, strontium chloride, and the like. Since the present invention allows for prolonged contact via the use of an appropriate tray and/or a sticky composition, desensitizing agents in the composition are able to penetrate through the enamel.
In a preferred embodiment, the opacifying dental compositions within the scope of the present invention will be sufficiently sticky and generally viscous such that positive pressure is needed to dispense them from the container; gravity is not sufficient. Unlike conventional low-viscosity compositions such as GLY-OXIDE (manufactured by Marion Laboratories) or PROXIGEL (manufactured by Reed and Carnick according to U.S. Pat. No. 3,657,413 to Rosenthal), preferred whitening compositions according to the present invention will be packaged within a syringe, squeezable tube, or other similar positive pressure dispensing device.
An improved dental tray that is thin-walled, flexible and lightweight for holding the dental composition adjacent to a person""s teeth is preferably used in combination with sticky and viscous dental whitening compositions of the present invention. The general process for preparing such dental trays is as follows. First, an alginate impression which registers all teeth surfaces plus the gingival margin is made and a stone cast is made of the impression. Optional reservoirs can be prepared by building a layer of rigid material on the stone cast on specific teeth surfaces to be treated. A dental tray is then vacuum formed from the modified cast using a thin, flexible plastic sheet material. Once formed, the tray is preferably trimmed barely shy of the gingival margin on both the buccal and lingual surfaces of the person""s teeth. The resulting tray provides a comfortable fit of the person""s teeth with optional reservoirs or spaces located where the rigid material was placed on the stone cast. The trays can optionally overlap the gums if desired to provide contact between the dental compositions and a person""s gums. The trays of the present invention have greatly increased comfort and exert little or no significant mechanical pressure on a person""s teeth or gums. Instead, sticky dental compositions within the scope of the invention can act like a glue to hold the improved trays in place.
The amount of tooth whitening obtained through the use of the inventive compositions and methods is dependent primarily upon (1) the length of time each day the tray is worn; and (2) the number of days the tray is worn. The treatment schedule may be tailored to each person""s lifestyle or response to the treatment and can be performed as often as a person desires to provide effective relief from excessively translucent teeth. It has been found that treatment during sleep is a good treatment period since there is less mouth activity which causes less whitening composition to be pumped from the tray.
Accordingly, an object of the present invention is to provide compositions and methods for treating excessively translucent teeth.
It is another object to provide compositions for treating excessively translucent teeth which can optionally include other dental agents, such as bleaching agents, antimicrobial agents or anticariogenic agents.
It is a further object to provide compositions for bleaching teach that include a desensitizing agent for offsetting the tendency of peroxide bleaching agents to make teeth more sensitive.
Finally, it is an object and feature of this invention to provide compositions for treating excessively translucent teeth that are sufficiently sticky and resistant to dilution by saliva such that they have the ability to adhere and retain a flexible, thin-walled dental tray against a person""s teeth, wherein the dental tray does not exert significant mechanical pressures onto the person""s teeth or gums.
These and other objects and features of the present invention will become more fully apparent from the description as follows, or may be learned by the practice of the invention.